Shore Power Voltage Drop

[Hooked on Deanna]

Need Help....

I have been experiencing intermitten low voltage at my panel when under load. The voltage drop is from 120V to under 100V with no more than 10 amps of load. My AC on my "new to me cruiser" shuts down when voltage drops below 100V. I split off one 30amp x 50ft cord and both sides of my panel reads the same (normal or low).

When I get low voltage readings and fire up the genny the problem goes away. I'm not good with electrical repairs and only own a MM but dont own a line voltage meter.

The voltage drops with any of my higher load equipment like my hot water heater. My marina neighbors do experience voltage flucation but don't complain about being able to run their AC or other equipment within a certain load amount.

Does anyone think this is a boat problem or shore power issue at my marina? What is a good trouble shooting process. I will buy a meter to check line voltage if that is recommended.

 

[Fireman431]

Re: Shore Power Voltage Drop

Take it to another marina and see if the problem happens there, too.

 

[Hooked on Deanna]

Re: Shore Power Voltage Drop

Sometimes I can switch to my neighbors outlet and it works when mind doesn't and vice versa. Other than checking at another marina what else can I check (going on a cruise and don;t want this ti be an issue).

 

[Don S]

Re: Shore Power Voltage Drop

After living aboard in the PNW and SE Alaska for 12 years, I would suggest you look at the plugs on the cord and the inlet on the boat. Over time the contacts can become loose or corroded and cause poor contact. Any indication of melting plastic around the connections is a sign of problems.
Low voltage happens just before total failure.

 

[bassman284]

Re: Shore Power Voltage Drop

Sometimes I can switch to my neighbors outlet and it works when mind doesn't and vice versa. Other than checking at another marina what else can I check (going on a cruise and don;t want this ti be an issue).

Want to get this straight. By vice versa, do you mean that sometimes your neighbors outlet works and sometimes it doesn't? Or do you mean that you neighbor hooks to yours and it sometimes works and sometimes doesn't?

 

[Hooked on Deanna]

Re: Shore Power Voltage Drop

Yes - sometimes it works and sometime my neighbors outlet doesn't (on the same power post).


I looked at the outlets cleaned and greased them with no change.

 

[Woodnaut]

Re: Shore Power Voltage Drop

Yes - sometimes it works and sometime my neighbors outlet doesn't (on the same power post).


I looked at the outlets cleaned and greased them with no change.

Sounds like power at the dock post might be dropping. If you are qualified to safely measure the voltage, then consider measuring the voltage on the dock at one connector while a boat is plugged in and under full load on the other connector. Compare that to a voltage reading on the dock with neither boat plugged in. Safety first - do not attempt this unless you have a good voltmeter and are comfortable using it in a safe manner.

 

[Hooked on Deanna]

Re: Shore Power Voltage Drop

I've struggled with whether or not I should purchase a MM with a line tester, as I'm afraid I'll try to do further trouble shooting and mess up. My marina has promised for a few weeks to get an electrician to look at my power. If it is the marina I'm screwed (close to my home), but I'm afraid of a boat problem also.

 

[Woodnaut]

Re: Shore Power Voltage Drop

I've struggled with whether or not I should purchase a MM with a line tester, as I'm afraid I'll try to do further trouble shooting and mess up. My marina has promised for a few weeks to get an electrician to look at my power. If it is the marina I'm screwed (close to my home), but I'm afraid of a boat problem also.

Always best to play it safe if you have any concerns whatsoever.

 

[Fireman431]

Re: Shore Power Voltage Drop

Have you tried other power posts at the same marina, but different docks? More than likely the problem is in either your power stanchion or your cords.

 

[Bridar]

Re: Shore Power Voltage Drop

Have you tried a different shoreline? Why are you using a 50ft length? When you checked your connections, did you check all the connections to your ground bar?

 

[fucawi]

Re: Shore Power Voltage Drop

if its a dual outlet on the stanchon ..then plug in the left one ...and measure the volts at the right hand one...safe and easy ....then swop over and test again ...if you have less than 115 v then the marina is giveing you a bad supply ....hope you have your earth leakage detectors in place and if the boat is metal anti corrosion system in place ....one foot on a live boat and one on the dock is fatal .....I always jump !!!

 

[sjohnson44]

Re: Shore Power Voltage Drop

You will see voltage drop in a short to ground as well. Although when I say short to ground, it may not be a direct short. If it was, then a breaker of some sort should open somewhere. However, it could be leaking through a water soaked cable, or broken strands of wire touching a ground.

First place to look would be any wiring that gets moved a lot, or something that gets plugged in and out often as well. If all of your equipment suffers then expect problems with the main line in your boat, and if not that then the marinas power.

A digital multimeter is always a great tool to have and your basic ones can be had for around $20.
If you do happen to get one, I would start by checking continuity or resistance (ohms) from the hot leg of the boats plug, to the ground on the same plug.

This test will tell you if there is anything shorted to ground on your boat. The meter should display a number reading in ohms. If you get a reading of less than or equal to 100ohms, then you can assume that there may be a problem with your boat. However, it should display OL (open loop), meaning there is no path from hot lead to ground. If it does display OL, then it is safe to say you are not at fault.

Note: You should only check for continuity while power is off. Never check for continuity between two sources if either is energized, you could damage a sensitive device on the other side of the line.

I hope this helps for what little I can help. Good luck

 

[fucawi]

Re: Shore Power Voltage Drop

A short will blow your fuses or trips ...you cannot have half a short...check the supply voltage first ..easy and safe to do ...even a 120v bulb in the adjacent socket will dim badly if its as bad as you say .

 

[Cap’n Ray]

Fucawi- I have to disagree with your 'half a short' statement. You can have a high resistance short (1/2 a short) to ground or neutral that will draw power and not blow a fuse. A 'dead short' will almost always blow a fuse/ pop the breaker, but high-resistance short is usually what you get when something is about to fail completely, or in the process of it. on a safety note... A 'half short' or high resistance short, or any other description of this situation on a boat WILL CREATE A LETHAL SITUATION! PLEASE rule out a short of ANY sort on your boat. That being said, it does sound like a problem with the plugs, cables or marina outlets with the 'sometimes it works, sometimes it doesn't' troubleshooting so far. Best of luck, and be safe!

 

[Hooked on Deanna]

Re: Shore Power Voltage Drop

Ok...Thanks for all the input.

I have used my outlet tester (circle, triangle, square) and the lighted symbols suggest I'm good. I will try another marina or power post test with my Honda genny. If I get low volts from shore power when under load and switch to my genny (plug my shore power cord into it) and things look good that would suggest a marina issue.

Going to the boat shortly I will post my findings tonight.

Thanks!

 

[Hooked on Deanna]

Re: Shore Power Voltage Drop

Test complete - Shore power dropped to 100V with 10 amp load from hot water heater. Connected my 2000W Honda genny to my power cord and the Volts didn;t drop under the same load. So I guess that establihes the power source as the problem. Will call the power company to check their side side for possible cause. Thanks for the help.

 

[Woodnaut]

Re: Shore Power Voltage Drop

Thanks for following up and posting your findings on this topic! Hope it gets sorted out.

 

[fucawi]

Re: Shore Power Voltage Drop

never found a half short in 40 years . and you would need a Megger to test it ( 500v genertor ) ..if its wired to standard then a trip will click out ...100v at the stanchon at 2 kw is bad ...must be a lot of heat generated somewhere

 

[hrdwrkingacguy]

Re: Shore Power Voltage Drop

yea, there is no such thing as half a short...Something can be shorted, or grounded, they are two totally different things...I would bet on a loose neutral somewhere between the power post and the panel...

Shorts and grounds both blow fuses...